Tropical Depression THIRTEEN-E (Text)

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TROPICAL DEPRESSION THIRTEEN-E DISCUSSION NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP132009
800 PM PDT FRI AUG 28 2009
CONVENTIONAL SATELLITE IMAGERY INDICATES THAT THE AREA OF LOW
PRESSURE LOCATED SOUTH-SOUTHWEST OF ACAPULCO HAS ACQUIRED
SUFFICIENT ORGANIZED CONVECTION TO BE CLASSIFIED AS A TROPICAL
DEPRESSION. A 2030 UTC AMSR-E MICROWAVE IMAGE FROM THE NAVAL
RESEARCH LABORATORY MONTEREY SHOWS A WELL-DEFINED CURVED BANDING
FEATURE OVER THE WEST SEMICIRCLE OF THE CYCLONE. SUBSEQUENTLY...
WATER VAPOR IMAGERY REVEALS DIFFLUENT EASTERLY FLOW OVER THE
AFOREMENTIONED PORTION OF THE SYSTEM. THE INITIAL INTENSITY IS
ESTIMATED TO BE 30 KT IN AGREEMENT WITH THE DVORAK SATELLITE
INTENSITY ESTIMATES. THIRTEEN-E APPEARS TO BE WITHIN AN
ATMOSPHERIC AND OCEANIC ENVIRONMENT FAVORABLE FOR STRENGTHENING...AS
THE WATER IS WARM AND THE SHEAR IS LOW. THE OFFICIAL FORECAST
INDICATES INTENSIFICATION AT A CLIMATOLOGICAL RATE AND SIMILAR TO
THE INTENSITY MODEL CONSENSUS ICON. A GRADUAL WEAKENING NOTED AT
DAY 5 AS THE SYSTEM BEGINS TO MOVE OVER SLIGHTLY COOLER WATER
SOUTHWEST OF THE COAST OF BAJA CALIFORNIA.
THE DEPRESSION IS MOVING IN A GENERAL WESTWARD MOTION...280/10. A
MID-LEVEL TROPOSPHERIC RIDGE EXTENDING WESTWARD OVER CENTRAL MEXICO
SHOULD STEER THIRTEEN-E MORE TOWARD THE WEST-NORTHWEST DURING THE
NEXT 48 HOURS WITH A SLIGHT DECREASE IN FORWARD SPEED. THROUGH THE
REMAINING FORECAST PERIOD...THE DYNAMICAL MODELS ARE IN FAIR
AGREEMENT IN WEAKENING THE RIDGE AND MOVING SHIFTING IT EASTWARD IN
RESPONSE TO A MID/UPPER LEVEL TROUGH APPROACHING FROM THE
NORTHWEST. THIS CHANGE IN THE STEERING PATTERN IS EXPECTED TO
GRADUALLY TURN THE CYCLONE TOWARD THE NORTHWEST WHILE INCREASING
THE ITS FORWARD MOTION. THE GLOBAL AND HURRICANE MODELS ARE
ESSENTIALLY SEPARATED INTO TWO CLUSTERS. THE FIRST CLUSTER CONSISTS
OF THE GFDL/HWRF AND IS TO THE RIGHT OF THE TVCN CONSENSUS...WITH
BOTH SUGGESTING A CONSIDERABLY STRONGER SYSTEM WITH LESS RIDGING TO
THE EAST. THE SECOND CLUSTER CONTAINING THE GFS/NOGAPS/UKMET/ECMWF
RESIDES TO THE LEFT OF THE TVCN. THESE PARTICULAR MODELS INDICATE A
WEAKER SYSTEM MOVING WEST-NORTHWESTWARD SOUTH OF A STRONGER LOW TO
MID-LEVEL RIDGE. THE OFFICIAL FORECAST IS WEIGHED HEAVILY ON THE
TVCN DYNAMICAL MODEL CONSENSUS AND IS A COMPROMISE BETWEEN TWO
MODEL CLUSTERS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 29/0300Z 13.8N 101.9W 30 KT
12HR VT 29/1200Z 14.1N 102.9W 40 KT
24HR VT 30/0000Z 14.5N 104.4W 45 KT
36HR VT 30/1200Z 14.9N 105.7W 55 KT
48HR VT 31/0000Z 15.4N 106.9W 65 KT
72HR VT 01/0000Z 17.5N 109.5W 75 KT
96HR VT 02/0000Z 20.5N 112.0W 75 KT
120HR VT 03/0000Z 23.5N 114.0W 65 KT
$$
FORECASTER ROBERTS/BEVEN
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